I'll dwell on this topic for a little longer than the other types of numbers. In Perl you can specify not only decimal numbers, but also numbers in hex, octal, and binary. If you are not familiar with how these systems work, you can try these Wikipedia articles:

Extra!
The modulus operator (%) can be used to find the remainder when dividing two numbers.
If that doesn't make sense now, that's fine, it's not that important. (Note, this returns 0 when used on floating point numbers)